Relaxation chair comprising a flexible support element of the user jointly borne by a back-rest and a seat articulated on one another and mounted movably with sliding on a frame

ABSTRACT

Relaxation chair comprising a flexible support element of the user jointly borne by a back-rest and a seat articulated on one another and mounted movably with sliding on a frame The relaxation chair of the present invention comprises a bearing structure of a flexible support element of the user&#39;s body arranged as a seat element and a back-rest element articulated with respect to one another. This bearing structure is guided in sliding on a frame by means of guide rails respectively associated to the seat and back-rest elements. The seat element is for example in the form of a U-shaped frame with a bottom free edge and lateral connecting bars. The seat element comprises an inflection between the bottom free edge and the corresponding articulation end so that the flexible support element is kept at a distance from the bearing structure, above the seat element, including when the user is installed in the chair.

BACKGROUND OF THE INVENTION

The invention relates to the field of furniture and more particularly to the field of chairs mainly comprising a seat and a back-rest defining together a dihedron to receive the user's body.

The object thereof is to provide a relaxation chair arranged to make the angle of the dihedron formed between the seat and back-rest vary, from a movement of the body of the user installed on the chair.

It concerns a relaxation chair comprising a frame for the chair to rest on the ground, a flexible support element for supporting a user, articulation means of the flexible support element with respect to the frame, the articulation means comprising a bearing structure comprising a seat element and a back-rest element, supported by the frame, articulated on one another and comprising sliding means running along guiding paths bounded by corresponding rails fixed onto the frame.

STATE OF THE ART

A chair is commonly composed of a seat and a back-rest defining between them a dihedron to receive the body of a user. Among the chairs, relaxation chairs organized to enable the angle of the dihedron to be varied to adapt it to the comfort sought for by the user are more particularly known.

In conventional manner, the chair comprises a seat element and a back-rest element, articulated pivotally on one another and respectively associated to the seat and back-rest of the chair. Easily reversible immobilization means enable the seat and/or back-rest to be held in place with different inclines desired by the user, according to the more or less supine posture in which he wishes to be supported by the chair.

According to a first type of relaxation chair, the latter is mainly composed of a frame bearing rigid elements respectively forming the seat and back-rest. One at least of these elements is supported in articulated manner by the frame to give the rigid elements a relative inclination mobility.

According to a second type of relaxation chair, a support part of the user's body is a flexible element, such as a canvas sheet or similar, forming the seat and back-rest. This sheet is fixed at each of its bottom and top ends to rigid elements of a frame, respectively associated to support of the seating zone and of the back-rest zone of the sheet. These rigid elements are articulated on one another in their middle zone to bear jointly on the ground and to enable the general orientation of the sheet with respect to the bearing plane of the chair on the ground to be modified.

A problem arising for relaxation chairs lies in the possibility provided for the user to modify the angle of the dihedron defined by the seat and back-rest easily and quickly. More precisely, such a modification of the angle can be constraining both in terms of the operation involving adjustment of the amplitude of this angle and of the operation consisting in subsequently immobilizing the movable elements.

The document WO-A-9416600, in particular, describes a chair that is adjustable by the movements of a user's body. The chair comprises a seat and a back-rest constituting a flexible support part of the user. The seat and back-rest are mounted pivoting with respect to one another on two lateral support elements respectively of the seat and back-rest. The chair also comprises a frame comprising a pair of guide rails for tenons securedly fixed to the lateral support element of the seat and a pair of guide rails for tenons securedly fixed to the lateral support element of the back-rest. The guide rails of the seat are curved, of circular shape and face upwards.

However, in reality, the chair cannot operate without the assistance of jacks, which constitute balancing and braking means. The necessary presence of these jacks considerably increases the production cost of the chair. Moreover, the flexible support part of the user is secured on each side and over their whole length by the lateral support elements. They are also held by the articulation points of their lateral elements. There is therefore no possibility of extension of the flexible support part when the chair is made to move. This results in a large discomfort for the user and makes it very difficult to return the chair to its original position.

OBJECT OF THE INVENTION

The object of the present invention is to remedy the above-mentioned drawbacks and to propose a relaxation chair enabling the angle of the dihedron formed between the seat and back-rest elements of the chair to be modified quickly and to keep the latter in position, by means of a simple and single movement performed naturally by the user with his body against these elements.

This object is achieved by a chair according to the appended claims and, more particularly, by the fact that:

-   -   the seat element comprises a bottom free edge, securedly fixed         to at least one seat connecting bar comprising an articulation         end,     -   the back-rest element comprises a top free edge, securedly fixed         to at least one back-rest connecting bar comprising an         articulation end,     -   the flexible support element is fixed to the free edges of the         seat and back-rest elements,     -   the seat element comprises at least one inflection, between the         bottom free edge and the corresponding articulation end, so that         the flexible support element is kept at a distance from the         bearing structure, above the seat element, including when the         user is installed in the chair.

DESCRIPTION OF THE FIGURES

Other advantages and features will become more clearly apparent from the following description of particular embodiments of the invention given as non-restrictive examples only and represented in the accompanying drawings, in which:

FIG. 1 and FIG. 2 each represent a perspective view of a particular embodiment of a flexible support element of a relaxation chair according to the invention.

FIG. 3 represents a perspective view of a particular embodiment of a bearing structure of a relaxation chair according to the invention.

FIG. 4 schematically represents a side view of a particular embodiment of a relaxation chair according to the invention, illustrating different positions of the bearing structure.

FIG. 5 schematically represents a side view of an alternative embodiment of a relaxation chair according to the invention, illustrating different positions of the bearing structure.

FIG. 6 to FIG. 10 schematically represent a side view of the relaxation chair according to FIG. 5, illustrating different successive positions of the chair between its extreme folded and extended positions.

FIG. 11 represents a perspective view of an alternative embodiment of a bearing structure of a relaxation chair according to the invention.

FIG. 12 represents a side view of the bearing structure according to FIG. 11.

FIG. 13 represents a side view of an alternative embodiment of a bearing structure of a relaxation chair according to the invention.

DESCRIPTION OF PARTICULAR EMBODIMENTS

The relaxation chair according to the invention is mainly composed of a frame (not shown) supporting a bearing structure 1 of a flexible support element 2 of the user's body.

In FIGS. 1 and 2, the flexible support element 2 is formed by a wall deformable between the bottom end 3 and top end 4 thereof, said ends 3 and 4 being equipped with fixing means 5 for fixing to the bearing structure 1. The flexible support element 2 is notably able to be deformed at the level of its global surface, in a plane orthogonal to the bearing plane of the chair on the ground.

In FIG. 1, the flexible support element 2 is composed of two rigid frames 6 and 7 articulated freely on one another. The internal space bounded by each of the frames 6 and 7 is provided with elastically deformable suspension elements, such as springs or slats. These suspension elements are anchored at their lateral edges onto uprights of the frames 6 and 7. For the top frame 6, these suspension elements are formed by wires 8 arranged as springs, whereas for the other frame 7, the suspension elements are formed by slats 9. These elements 8 and 9 are described to serve as non-restrictive examples only and can be transposed at will from one of the frames 6 and 7 to the other. In FIG. 2, the flexible support element 2 is composed of slats 10, 11, assembled to one another by lateral straps 12.

As an alternative, the flexible support element 2 can be formed by a canvas sheet or similar, by a cloth comprising braided straps or by transverse slats supported by lateral straps.

In FIG. 3, the bearing structure 1 globally comprises a seat element 13 and a back-rest element 14 each formed by a frame substantially in the shape of an inverted U and arranged in the extension of one another so as to define a dihedron for receiving the user's body.

The seat element 13 comprises a bottom free edge 18 securedly fixed to two lateral seat connecting bars 16 substantially perpendicular to the bottom free edge 18 and each comprising an articulation end. The back-rest element 14 comprises a top free edge 19 securedly fixed to two lateral back-rest connecting bars 17 and each comprising an articulation end.

The seat element 13 and back-rest element 14 are abutted at the level of the articulation ends of their corresponding connecting bars 16, 17 and articulated with respect to one another around the articulation axis 15 to enable a variation of the angle of the dihedron that they bound and define together. The flexible support element 2 is designed to be fixed onto the corresponding bottom free edge 18 and top free edge 19 of the seat element 13 and back-rest element 14.

Both the seat element 13 and back-rest element 14 are equipped with sliding means 20, 21, 22, such as rollers, slide racks or the like. A single sliding means can be composed of several associated elemental sliding means. The sliding means 20, 21, 22 are positioned on the lateral connecting bars 16, 17 of the seat element 13 and back-rest element 14 to operate in conjunction with respective rails 23 and 24, securedly fixed to the frame, bounding guiding paths of the sliding means 20, 21, 22 (FIGS. 4 and 5). The seat element 13 comprises a couple of distinct sliding means 21 and 22, whereas the back-rest element 14 only comprises a single sliding means 20.

Furthermore, the sliding means 20, 21, 22 of the seat element 13 and back-rest element 14 advantageously form stop means at the end of the rail, against the travel of the seat element 13 and back-rest element 14, in the extreme extended (FIG. 10) and folded (FIG. 6) positions of the bearing structure 1.

To make the chair 1 move, the operation consists in the user pressing against the seat element 13 and the back-rest element 14 of the bearing structure 1 by means of the flexible support element 2. This results in the flexible support element 2 being tensioned and deforming so as to take the exact shape of the user's body. A slight pressure of the user's shoulders combined with an alleviation of the pressure of the pelvis by pressing on his heels then results simultaneously in sliding of the seat element 13 and of the back-rest element 14 along the corresponding rail. By stopping the pressure exerted by his back, the user stops the movement of the chair in the required position.

Securing the seat element 13 and back-rest element 14 in the required position with respect to one another results from the bearing taken by the sliding means 20, 21, 22 of the seat element 13 and the back-rest element 14 against the corresponding guide rails 23, 24.

The angle variation of the dihedron is a continuous value variation between the extreme positions of the seat element 13 and the back-rest element 14 corresponding to the extended position (FIG. 10) and folded position (FIG. 6) of the bearing structure 1.

Thus, when the chair is made to move, the flexible support element 2, which is fixed onto the free edges 18, 19 of the seat element 13 and back-rest element 14, extends between the two free edges 18, 19 during the opening movement of the bearing structure 1 and frontward sliding thereof. This results in free extension of the flexible support element 2 and increasing tensioning thereof.

The relaxation chair thus provides optimum comfort. This comfort results from the user's body being supported the flexible support element 2. It also results from the continuous value variation of the angle of the dihedron defined between the seat element 13 and the back-rest element 14 of the chair. This comfort moreover and especially results from the simplicity and ease of the operation whereby the angle of the dihedron is able to be modified, achieved by the pelvis and/or back of the user simply pressing against the corresponding element of the bearing structure 1. Such a pressing naturally causes not only said angle variation but also immobilization in any position of the seat element 13 and back-rest element 14 with respect to the frame.

In FIGS. 4 and 5, the frame of the chair is equipped with guide rails 23 and 24 of the sliding means 20, 21, 22 of the seat element 13 and back-rest element 14. In FIG. 4, the frame comprises a guide rail 23 for the back-rest element 14 and a guide rail 24 for the seat element 13. The guide rail 23 of the back-rest element 14 defines a single guiding path for the corresponding sliding means 20 whereas the guide rail 24 of the seat element 13 defines two concurrent paths for respective guiding of the sliding means 21 and 22 of the seat element 13.

In FIG. 4, the guide rail 24 associated to the seat element 13 is a single rail curved upwards at its ends, whereas in FIG. 5, the guide rail 24 associated to the seat element 13 is composed of a front elemental guide rail 25 and a rear elemental guide rail 26, close to the articulation axis 15.

The guide rail 23 associated to the back-rest element 14 is inclined with respect to the horizontal, i.e. with respect to the bearing plane of the frame on the ground, by an angle D (FIG. 5) of about 450° to 55°, for a length of guide rail 23 of about 220 mm.

The guide rail 23 is fixed onto the frame in a zone corresponding to the middle zone of the back-rest element 14, located between the top free edge 19 and the corresponding articulation end. More particularly, the guide zone of the back-rest element 14, by means of the corresponding guide rail 23, is located between the bearing zones of the user on the flexible support element 2, and in particular underneath the bearing zone of the back and above the bearing zone of the pelvis.

Moreover, the guide rail 23 of the back-rest element 14 performs a “back to the wall” function, i.e. it eliminates the recoil of the back-rest during the rocking movement of the latter. This enables the articulated bearing structure 1 to move forward during its extension and to eliminate recoil of the back. The chair can thus be placed against a wall without hampering its rocking movement.

The length and angle of incline of the guide rail 23 of the back-rest element 14 are determined taking into account, in a first instance, the dimensional constraints of the chair, the guide rail 23 preferably having to be masked. In addition, they take into account the length and angle of incline of the guide rail 24 (FIG. 4), or of the elemental guide rails 25 and 26 (FIG. 5), of the seat element 13. They also take into account the position of the different sliding means 20, 21, 22 of the bearing structure 1 and, in particular, the position of the front sliding means 21 associated with the seat element 13.

In FIGS. 5 to 10, the front elemental guide rail 25 and rear elemental guide rail 26 of the seat element 13 are substantially straight and inclined in opposition with respect to the horizontal.

The rear elemental guide rail 26 is notably inclined downwards, in the direction of the front of the chair, with respect to the horizontal, i.e. with respect to the bearing plane of the frame on the ground, by an angle A of about 5° to 9° (FIG. 5), whereas the front elemental guide rail 25 is inclined upwards, in the direction of the front of the chair, by an angle B of about 2° to 6° (FIG. 5).

Furthermore, the front elemental guide rail 25 can be inflected to the front and upwards from the chair so as to form at its front end an angle C of about 8° to 12° with the horizontal (FIG. 5). This then gives the bearing structure 1 an accentuation of the backward rocking effect at the same time as extension thereof takes place.

According to an example of an embodiment relating to a chair of common dimensions, the rear elemental guide rail 26 has a length of about 310 mm, the front elemental guide rail 25 has a length of about 320 mm, and the back-rest guide rail 23 has a length of about 220 mm.

In this example of an embodiment, the rear sliding means 22 of the seat element 13 is situated about 40 mm from the articulation axis 15 of the seat element 13 and back-rest element 14, whereas the front sliding means 21 is situated about 310 mm to the rear of the bottom free edge 18 of the seat element 13. The sliding means 20 associated with the back-rest element 14 is for its part located in a middle zone between the top edge 19 and the corresponding articulation end of the back-rest element 14.

The opposite slopes of the rails front elemental rail 25 and rear elemental rail 26 of the seat element 13, the slope of the guide rail 23 of the back-rest element 14 and the relative positions of the sliding means 20, 21, 22 on the bearing structure 1 enable the angle of the seat to be controlled and create a self-balancing effect of the chair, which remains stable in any of its positions. Any blocking accessory of the chair is therefore rendered unnecessary when the user stops the chair at any point of its travel. This gives a genuine ease of use and a simplicity of manufacturing generating cost savings.

As represented in FIG. 3, the seat element 13 and back-rest element 14 comprise at least one inflection zone, respectively 27 and 28, to keep the flexible support element 2 at a distance from the elements 13 and 14. The inflection zones 27, 28 of the seat element 13 and back-rest element 14 are arranged between their free edge 18,19 and their corresponding articulation end.

In the particular embodiment represented in FIG. 3, the inflection 27 of the seat element 13 is preferably located close to its bottom edge 18 and the inflection 28 of the back-rest element 24 is preferably located at the level of the middle zone of the lateral connecting bars 17 of the back-rest element 14.

The flexible support element 2 is therefore kept at a distance from the bearing structure 1, above the seat element 13 and to the front of the back-rest element 14, including when the user is installed in the chair.

In FIGS. 6 to 10, different successive positions of the bearing structure 1 are represented. The characteristic movements of the bearing structure on the frame are notably obtained by means of the articulation of the bearing structure 1 on the frame and by means of the specific sliding assembly constituted by the three sliding means 20, 21 and 22 forming the bearing points of the bearing structure 1 on the frame.

The flexible support element 2 in practice constitute the operating means, causing sliding of the seat element 13 and back-rest element 14 on the frame. The inflections 27, 28 of the elements 13 and 14 enhance deformation and mobility of the flexible element 2, such as rocking and flexing thereof. This results in the flexible support element 2 accompanying the movements of the user's body when the bearing structure 1 is maneuvered.

A slight push exerted by the user with his shoulders on the flexible support element 2, combined with a frontward movement of the pelvis, cause an advance by sliding of the bearing structure 1 and extension thereof. Stopping such a push enables the bearing structure 1 to be naturally immobilized in a desired position. The faculty provided of continuous variation of the positions of the bearing structure 1 can be noted, so that each user, according to his morphology and his mood, can find the position that suits him best, from the vertical posture in the extreme folded position of the bearing structure 1 (FIG. 6) to a supine posture in the extreme extended position of the bearing structure 1 (FIG. 10).

When the bearing structure 1 is in any extended position, the user makes a slight corresponding movement to stand up, relieving his back in the frontward direction. Without him making any other movement, the bearing structure 1 slides along the frame to its extreme folded position (FIG. 6).

Such a result is particularly achieved from a suitable combination between the positions of the sliding means 20, 21, 22 on the bearing structure 1, the length, shape and position of the guide rails 23, 25, 26 on the frame and the shape of the seat element 13 and back-rest element 14 on the bearing structure 1. Such a combination makes in particular for ease of sliding of the bearing structure 1 on the frame in translation and in rocking, causing an increasing tensioning of the flexible support element 2 during the extension phase of the bearing structure 1. This results in the folding movement of the bearing structure 1 being automatic, due to the return torque exerted by the bearing structure 1, which is kept in suspension on the frame when it slides towards the folded position (FIG. 6).

Furthermore, the position of the front sliding means 21 of the seat element 13 determines the maximum extension opening of the bearing structure 1, on account of its participation in means for making said structure 1 come up against a stop at the end of the front elemental rail 25. The position of the front sliding means 21 also determines the degree of rocking of the seat element 13, causing rocking of the bearing structure 1 and the leverage effect necessary to make backward sliding of the bearing structure 1 automatic.

The incline and length of the rails therefore enable specific adjustment according to the type of comfort sought for. The feeling of comfort is different depending on the position of the chair, which generates a richness of use.

In FIGS. 11 and 12, the alternative embodiment of the bearing structure 1 differs from the previous embodiments by the shape of the seat element 13 and back-rest element 14. The seat element 13 comprises the bottom free edge 18, securedly fixed to a central seat connecting bar 16, forming a substantially T-shaped frame with the bottom free edge 18.

The central connecting bar 16 is preferably a substantially flat board and presents an end articulated around the axis 15 with respect to the back-rest element 14. The seat element 13 comprises an inflection 27 located between the bottom free edge 18 and the corresponding articulated end, preferably close to the articulated end, designed to keep the flexible support element 2 at a distance from the bearing structure 1, above the seat element 13, including when the user is installed in the chair.

The back-rest element 14 comprises the top free edge 19, securedly fixed to a central back-rest connecting bar 17, forming a substantially T-shaped frame with the top free edge 19. The central connecting bar 17 is preferably a substantially flat board and presents an end articulated around the axis 15 with respect to the seat element 13.

The central connecting bars 16 and 17 are substantially perpendicular to the corresponding free edges 18, 19 (FIG. 11). As before, the flexible support element 2 is fixed onto the bottom free edge 18 and top free edge 19. In the particular embodiment represented in FIG. 12, the bottom free edge 18 and top free edge 19 are jutted out over the central connecting bars 16, 17 in the direction of the chair 1 so as to raise the flexible support element 2 with respect to the bearing structure 1.

Movement of the chair 1 is achieved, as before, with the sliding means 21, 22 of the seat element 13 associated with a guide rail, or two elemental guide rails, of the frame and the sliding means 20 of the back-rest element 14 associated with a corresponding guide rail of the frame.

The alternative embodiment of the bearing structure 1, represented in FIG. 13, differs from the embodiment of FIGS. 11 and 12 by the shape of the back-rest element 14. An inflection 28 is located in a middle zone of the back-rest element 14, between the top free edge 19 and the corresponding articulated end of the central connecting bar 17, preferably close to the sliding means 20.

In this case, the top free edge 19 is preferably positioned in the extension of the central connecting bar 17, and is not jutted out in the direction of the chair. The top free edge 19 is substantially of the same width as the bottom free edge 18 and substantially perpendicular to the central connecting bar 17. As before, the inflections 27 and 28 enable the flexible support element 2 to be kept at a distance from the bearing structure 1, above the seat element 13 and to the front of the back-rest element 14, including when the user is installed in the chair.

In FIGS. 11 to 13, the seat element 13 and back-rest element 14 are made of wood, the inflections 27, 28 forming broken lines. In non-represented alternative embodiments, the bearing structure 1 can be made of metal or plastic and the central connecting bars 16, 17 of the seat element 13 and back-rest element 14 can be shaped as tubes, the inflections 27 and 28 then forming curved lines.

Furthermore, the seat element 13 and back-rest element 14 can comprise flat surfaces 29 positioned facing the inflections 27 and 28 to facilitate sliding and prevent too large frictions between the flexible support element 2 and the seat 13 and back-rest 14 elements.

Such a bearing structure 1 with seat 13 and back-rest 14 elements constituting T-shaped frameworks, and a corresponding frame of complementary shape, can be easily integrated in any type of chair. Moreover, the inflection 27 provides optimum comfort and sliding flexibility when the adjustment movement of the chair is performed in.

Thus, by using U-shaped (FIG. 3) or T-shaped frames (FIG. 11), the seat 13 and back-rest 14 elements can be integrated in all styles of chair while remaining masked by the flexible support element 2, which presents a great aesthetic advantage.

The invention is not limited to the different embodiments described above. In particular, the flexible support element 2 are able to be formed by other similar alternative embodiments, provided that the structure chosen is deformable between its bottom end 3 and top end 4 via which the flexible support element 2 is fixed to the bearing structure 1, and enables the tensions to which the flexible support element 2 is subjected under the weight of the user to be transmitted to the corresponding edges of the seat 13 and back-rest 14 elements.

Whatever the shape of the seat 13 and back-rest 14 elements, the inflections 27 and 28 can take a different shape and position, so long as the inflections enable the flexible support element 2 to be raised with respect to the bearing structure 1.

The different angle and dimension values of the guide rails 23, 24, 25, 26 are given for indication purposes only, a variation of the dimensions of the bearing structure 1 correspondingly leading to variations of said angle and dimension values.

The chair can comprise accessory means for blocking the bearing structure 1 in any one of its positions to prevent a spontaneous modification of the angle of the dihedron when the chair is unoccupied. This spontaneous modification is notably liable to occur due to the effect of an inattentive person pressing on the top of the chair when the bearing structure 1 is in the folded position.

These blocking means can in particular be formed by a part forming an obstacle to sliding of the seat element 13 on the frame. The blocking means can be two co-operating engagement parts supported by the bearing structure 1 and the frame, said blocking means being implemented by means of a deliberate action by the user when he leaves the chair.

The chair can also comprise accessory means for sliding operation assistance of the seat element 13 and back-rest element 14 along the guide rails 23, 24 that are associated thereto. An electric jack can for example be fitted between the frame onto which it is fixed, for example by clipping, and a cross-member arranged on the seat element 13. These arrangements are designed to assist physically deficient or handicapped people, without however waiving from the general rule of the invention as set out with regard to the relative mobility of the seat element 13 and back-rest element 14 with respect to the frame. 

1. Relaxation chair comprising a frame for the chair to rest on the ground, a flexible support element for supporting a user, articulation means of the flexible support element with respect to the frame, the articulation means comprising a bearing structure comprising a seat element and a back-rest element, supported by the frame, articulated on one another and comprising sliding means running along guiding paths bounded by corresponding rails fixed onto the frame, relaxation chair wherein: the seat element comprises a bottom free edge, securedly fixed to at least one seat connecting bar comprising an articulation end, the back-rest element comprises a top free edge, securedly fixed to at least one back-rest connecting bar comprising an articulation end, the flexible support element is fixed to the free edges of the seat and back-rest elements, the seat element comprises at least one inflection, between the bottom free edge and the corresponding articulation end, so that the flexible support element is kept at a distance from the bearing structure, above the seat element, including when the user is installed in the chair.
 2. Chair according to claim 1, wherein the back-rest element comprises at least one inflection, between the top free edge and the corresponding articulation end, so that the flexible support means are kept at a distance from the bearing structure, to the front of the back-rest element, including when the user is installed in the chair.
 3. Chair according to claim 2, wherein the inflections are located close to the corresponding free edges of the seat and back-rest elements.
 4. Chair according to claim 2, wherein the inflections are located close to the corresponding articulation ends of the seat and back-rest elements.
 5. Chair according to claim 1, wherein the seat and back-rest elements each comprise a central connecting bar, substantially perpendicular to the corresponding free edge, so as to each form a T-shaped frame.
 6. Chair according to claim 1, wherein the seat and back-rest elements each comprise two lateral connecting bars, substantially perpendicular to the corresponding free edge, so as to each form a U-shaped frame.
 7. Chair according to claim 1, wherein the rail associated to the back-rest element is fixed onto the frame in a zone corresponding to the middle zone of the back-rest element, located between the top edge and the corresponding articulation end, so that the guide zone of the back-rest element is located between the bearing zones of the user on the flexible support element.
 8. Chair according to claim 7, wherein the rail of the back-rest element is substantially straight and inclined with respect to the bearing plane of the frame on the ground by an angle of about 45° to 55°.
 9. Chair according to claim 1, wherein the guide rail associated to the seat element is a single curved rail along which a couple of distant sliding means run.
 10. Chair according to claim 1, wherein the guide rail associated to the seat element is composed of two elemental rails, one front and one rear with respect to the chair, along which elemental rails run corresponding sliding means of the seat element that are respectively associated thereto, the elemental rails being substantially straight and inclined in opposition with respect to one another.
 11. Chair according to claim 10, wherein the rear elemental rail is inclined with respect to the bearing plane of the frame on the ground by an angle of about 5° to 9°, whereas the front elemental rail is inclined with respect to the bearing plane of the frame on the ground by an angle of about 2° to 6°.
 12. Chair according to claim 10, wherein the front elemental rail is inflected in the frontward direction by an angle of about 8° to 12°, with respect to the bearing plane of the frame on the ground.
 13. Chair according to claim 1, wherein the flexible support element is any one of a flat arrangement of transverse slats borne by lateral straps, and of rigid elements in the form of a frame articulated on one another the internal spaces whereof which they confine are respectively equipped with elastically deformable means.
 14. Chair according to claim 1, comprising accessory means for blocking the bearing structure in any one of its positions to prevent a spontaneous modification of the angle of the dihedron formed by the seat and back-rest elements, when the chair is unoccupied in the folded position.
 15. Chair according to claim 1, comprising accessory means for sliding operation assistance of the seat and back-rest elements along the rails that are associated thereto. 